In known wood processing machines used to convert logs into chips or flakes, it has been common for the machines to include one or more cutting members mounted either on the face of a rotating disc or on the circumferential surface of a rotating drum. During operation of the machines, wood members are guided or urged into the rotating disc or drum so that the knife-like cutting members cut away chips or flakes from the wood members, and the wood members are ultimately consumed.
Such prior art cutting members are typically configured to cut a rectangular or similar cross section in the wood members. However, many of these configurations do not allow for efficient cutting of the wood, as they require large surges of power during the cutting stage, which necessitates the use of large motors. Therefore such prior art devices tend to be large, heavy, and expensive.
Prior art devices also typically utilize cutting members which are partially recessed within the disc or drum. Although this configuration results in a structurally effective attachment between the cutting members and the disc or drum, it is disadvantageous if unprocessable foreign material is present with the wood. When such foreign material is encountered, prior art machines typically jam, and the risk of extensive and costly damage to the machine is high. One example of such recessed cutter mounting configurations is shown in applicant's U.S. Pat. No. 4,444,234 incorporated herein by reference, which discloses the use of a drum having a plurality of the knives mounted within recesses in a rotating drum.
The presence of unprocessable material is a particular problem in processing stumps, brush and other material of the kind remaining on the site or a logging operation. Wood "hogs" used to shred such material are subject to considerable down time and damage to cutting elements when the latter encounter rocks, metal or the like. Cutting members in the past have been expensive to manufacture and sharpen, and have been re-sharpened for additional use. Significant expenditures of time and money have been necessary to remove the cutting members, sharpen all their edges, and reinstall them into the machine. An example of such resharpenable cutting members is shown in applicant's U.S. Pat. No. 4,569,380, incorporated herein by reference, which discloses the use of a cutting element having a plurality of resharpenable cutting elements.
It has also been known to provide such wood processing machines with separating grates, which allow the passage of adequately-reduced wood chips out of the machine, but direct inadequately-reduced chips back to the input hopper to be processed further. These separating grates are typically formed out of a platelike material which defines a plurality of selectively-sized slots. Although these configurations are effective to a degree, they are prone to wear, which is disadvantageous in that the grate is typically of unitary construction, and replacement of the entire grate may be necessary in the case of an excessively worn grate. Finally, such prior art separating grates have limited effectiveness when processing wood which has a tendency to break up into elongate splinters, as such splinters may pass through the slots although their length is unacceptable.
Therefore it may be seen that a need has existed in the wood processing art for a cutting member which facilitates power-efficient cutting and shredding of wood products. It may also be seen that a need has existed for a wood processing machine which is subject to a minimum of damage when encountering unprocessable foreign material, and has disposable cutting members that can be replaced with a minimum of time and effort. Furthermore, a need has existed for a chip separating grate to be used in such wood processing machines which is resistant to wear, and does not allow the passage of wood chips having an unacceptable length.